Leaf Spot of Rhubarb Caused by Didymella rhei in Korea

Gyo-Bin Lee¹ Young-Moon Mo² Weon-Dae Cho¹ Wan-Gyu Kim^1,*

¹Global Agro-Consulting Corporation, Suwon 16614, Korea
²Ginseng & Medicinal Plant Research Institute, Gangwondo Agricultural Research and Extension Services, Cheolwon 24054, Korea

Abstract

During disease surveys conducted from 2019 to 2021 in Korea, leaf spot symptoms in rhubarb (Rheum rhabarbarum) plants were frequently observed in plants growing in fields located in Cheolwon, Taebaek, and Inje in Gangwon Province. The incidence of diseased leaves of the plants in the fields ranged from 2% to 80%. Nine single-spore isolates of Phoma sp. were obtained from lesions of the diseased leaves; all of them were identified as Didymella rhei based on their cultural, morphological, and molecular characteristics. Three isolates of D. rhei were tested for pathogenicity on rhubarb leaves using artificial inoculation. All the tested isolates caused leaf spot symptoms in the inoculated plants; the symptoms were similar to those observed in plants from the fields investigated. This is the first report of D. rhei causing leaf spot in rhubarb in Korea.

Figures & Tables

Fig. 1. Leaf spot symptoms in rhubarb plants. Symptoms observed in the fields investigated (A and B). Symptoms induced by artificial inoculation test with an isolate of (C). A non-inoculated plant (D).